I never use “Render to Disc”
It’s much better and safer to just hit the normal ‘Render’ button (the big one in the middle of the set of five spheres in the Left hand icon menu set.
When your render is complete, you can save the image in several formats from the File menu.
I, too, have never rendered to disk. However, it does have some value for long renders. David Brinnen explains in one of his videos I saw, (sorry I don’t remember the link, but who here could forget that name), that; by rendering to disk, should you get to a point where you have to stop the render and shut down your computer, once you have it all back running again, you can resume that render where it left off, simply by loading it back in and clicking the same button you would to resume a non-disk render.